Generally speaking you want as less as possible extra glass in front of your primary lens (the one that limits the resolution). Every single thing you put in front will degrade image a bit (although with high quality wide angle lens no one can spot the difference, but it's there), so stacking them up there might not be the best idea.

But as always: If you already have both put them on and look at the footage. If you (and whoever you're filming for) can't spot the difference then you're good to go :)

well done for the link ! So it might be possible, but i'm pretty sure the quality of lenses shown is better than the one I want to match (at least for the .55).

The idea is to get one lens for general purpose and one for inside jumps by adding a complement without dealing too much with quality. If the quality matches a baby death .3 then it'll be a still compact solution for a price in pair with a Royal .2

you don't get GREATER lines of resolution when stacking lenses, you get lesser resolution when stacking lenses. The lowest resolution determines the best of the end result. I have both, but don't have both with me (on Xmas holiday). I'll screw em' together. How well it works will be camera dependent. What's the end game?

I know that, I suppose that if you put two bezels together the result won't be bad. In this case, the .55 will be the worst and I assume some light/contrast can be lost too but... imagine if it's good or even fair ?

500 lines for the couple still gives a marvelous result for a real GA <.3 at this price.

you're assuming the focal points will perfectly line up (they may well not) and that would immediately impair the resolution, and you could easily be less than an SD-designed lens. When I get back to the DZ I'll shoot a lens chart with them stacked, and that'll put an end to speculation. I'm curious myself.

Decide for yourself if it works for you. The loss in resolution can't be measured in these images, but it's fairly apparent anyway. Note in the combined lenses there is also a lot of refraction. Some might like the look, but the vignetting, added distortion, and refraction make it a no-go for me except in some very weird circumstances.